National leader Simon Bridges has failed to make any headway with voters in the absence of Prime Minister Jacinda Ardern, although New Zealand First and the Green Party have had a slight bounce in the latest 1 NEWS Colmar Brunton poll.

The poll covers the period from July 28 to August 1, during which the National Party conference was held at Auckland's SkyCity convention centre.

The poll has National steady on 45 per cent support, the same as the last poll in May which was before Ardern took six weeks' leave to have her daughter.

Labour was down one point to 42 per cent, but the Greens and NZ First were both up a point, to 6 per cent and 5 per cent respectively. That puts NZ First right on the button for getting back into Parliament if an election was held now.

ACT and the Maori Party, which is not in Parliament, were also steady on 1 per cent support each.

In the preferred Prime Minister stakes Ardern was on 40 per cent, down one point on the previous poll. That slight drop could be written off as a reflection of her lack of profile in the past six weeks.

But her stand-in, Deputy Prime Minister and NZ First leader Winston Peters got a slight bump, up one point as preferred PM to 5 per cent.

But it was Simon Bridges, who arguably should have made some hay while the sun shone without the shadow of Ardern blocking it, who fared worst.

At a time when his profile should have been getting more attention – the end of his countrywide 'get to know me' tour and his upbeat, drum-beat video introducing himself to potential voters at the National Party conference – Bridges was down two points to just 10 per cent support as preferred PM.

That puts him back where he was in April, a month after taking over the leadership from Bill English.

Bridges said it was the party vote that determined the party's power, not the preferred prime ministership.

"That said, I don't take it lightly. I know that the prime ministership is not something anyone deserves to get on a platter, and I need to keep going out in what is relatively early days and start earning the trust of New Zealanders over time."

He didn't necessarily expect his performance at the National Party conference would have resulted in a boost as preferred prime minister, and the Government had made no headway since the Budget.

"National is still incredibly well-supported. I think that reflects a concern about the economy and the economic management of New Zealand and the sense of slowdown."

Ardern said she was pleased to see the Government as a whole with a strong lead over the opposition. The Coalition together is on 53 per cent support.

"Labour's vote is also holding up and more people than not are optimistic about the economy.

"These numbers were taken while I was on leave and, I think, really speak to the strength and stability of the Coalition and the plan we have," Ardern said in a statement.

On the economic outlook, optimism was down one point to 39 per cent while pessimism was steady on 35 per cent. This shows the negativity of business has not filtered through to voters.

The latest ANZ Business Outlook Survey, out last week, showed business confidence and firms' views of their own activity, continued to fall in July to reach their lowest levels since May 2008 and May 2009 respectively.

The 1 NEWS Colmar Brunton Poll sampled canvassed 1007 voters.